<!DOCTYPE html>
<html>

<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>无标题文档</title>
</head>

<style>
    * {
        font-size: 12px;
    }
    
    #bg1 {
        background-color: grey;
    }
    
    #bg2 {
        background-color: blue;
    }
    
    a.ys {
        color: red;
    }
    
    p {
        background-color: grey;
    }
    
    p.size,
    a.weilei {
        font-size: 30px;
    }
    
    a.weilei:hover {
        color: red;
    }
</style>

<body>
    <dl>
        <dt id="bg1">什么是HTML</dt>
        <dd>HTML是超文本标记语言</dd>
        <dd>HTML是写个浏览器的语言</dd>
    </dl>
    <dl>
        <dt id="bg2">什么是JavaScript</dt>
        <dd><a class="ys" href="#">Javascript</a>是在浏览器端的脚本语言</dd>
    </dl>
    <p>学习HTML</p>
    <p class="size">学习PHP,<a class="weilei" href="http://www.baidu.com">百度一下</a></p>
    <p>学习CSS</p>
</body>

</html>